All endings are painful to some degree some much larger than others. Have you ever noticed that most toddlers all of a sudden become very shy when they are told to say goodbye someone. Saying goodbye is a tiny ending but will cause some difficult feeling. Think about when you’ve gone out and had a great time, you don’t want it to end but eventually it has to.
Depending on ones emotional landscape some people will find it easier than others to manage endings. For some the vast amount of anxiety an ending brings up can stop or hinder being able to start something new.